Which vehicles are prohibited from using a road sign-posted like this?

This road sign indicates a prohibition for trucks. Specifically, it means that trucks with a permissible total mass exceeding 3.5 tons (option 1) and truck tractors (option 2) are not allowed to use this road. The sign does not apply to cars with trailers (option 3).

The key rule here is that the restriction targets heavier commercial vehicles, mainly to protect roads from damage, reduce traffic, or improve safety in certain areas. Cars with trailers are generally exempt from this particular restriction, as they are considered differently in traffic regulations.

So, whenever you see this sign, remember it specifically restricts trucks over 3.5 tons and truck tractors, but not smaller vehicles with trailers. This helps ensure safe and appropriate usage of certain roads.